Multiexchange automatic telephone system



April 10, 1951 P. BAKKER MULTIEXCHANGE AUTOMATIC TELEPHONE SYSTEMOriginal Filed May 4, 1942 5 Sheets-Sheet l v a-T/ O-*j f= f il@ 3372Exc/wmf 8-742 was ,4-7/ u/:D cc/ W 1 -o-n x l I4 EXC//A/YGEA A-T7 ./zla6 lfj/ EXCHANGE C Fry' .Ej/735.277

MA /l//AL EXcf/AA/Gfs #8 #o #o AUTO/VA r/c EXCHANGES INVENTOR.

A TTO/VEY April 10, 1951 P. BAKKER MULTIEXCHANGE AUTOMATIC TELEPHONESYSTEM Original Filed May 4, 1942 5 Sheets-Sheet 2 A from/5 y April l0,1951 P. BAKKER MULTIEXCHANGE AUTOMATIC TELEPHONE SYSTEM Original FiledHay 4, 1942 IN VEN TOR.

CL W 5 W A fro/WISY April '10, 1951 P. BAKKER 2,548,191

MULTIEXCHANGE AUTOMATIC TELEPHONE SYSTEM A TTO/VE Y April 10, 1951 P.BAKKER MULTIEXCHANGE AUTOMATIC TELEPHONE SYSTEM 5 Sheets-Sheet 5Original Filed May 4, 1942 hmmm. www:

Alage and its environs.

Patented pr. 10, 1951 MU LTIEXCHANGE AUTOMATIC TELEPHONE SYSTEM PierBakker, Chicago, Ill., assignor'to Kellogg Switchboard and SupplyCompany, Chicago, Ill., a corporation of Illinois Original applicationMay 4, 1942, Serial No.

441,641, now Patent No. 2,427,650, dated Septembcr 23, 1947. Divided andthis application October 26, 1945, Serial No. 624,783

6 Claims.

This invention relates to multi-exchange automatic telephone systems.Its main object is to provide new and improved circuit arrangementseffective on interexchange calls to, or through, a tandem exchange tocause a charge to be assessed against the calling subscriber, or forpermitting the call to be completed without charge, depending upon thedestination of the call. This application is a division of my priorapplication for Multi-exchange community automatic telephone systems,Serial No. 441,641, filed May 4, 1942, now Patent No. 2,427,650, issuedSeptember 23, 1947.

GENERAL DESCRIPTION As is explained in my parent application abovereferred to, the present invention is particularly suited for use in aso-called community automatic telephone system.

The term community automatic telephone system as used herein refers toan automatic telephone system arranged to provide telephone service in asmall community, usually a town or vil- A network ofA such exchanges maybe provided by interconnecting two or more of them by trunk lines toenable subscribers of any such exchange to call those of the otherexchanges.

Many problems are encountered in connection with community automaticexchanges which are y not commonly met with in the larger automaticexchanges provided in cities. For example, the lines interconnecting acommunity automatic exchange with another exchange are usually so smallin number that their eiiicient use requires each of them togbe equippedfor two-way operation, and to be equipped to furnish toll as well aslocal service. Moreover, Vthe number of lines served by such an exchangevis ordinarily so small (from a few dozen to two hundred, for example),and the offered trafc is consequently so small, that the eicient use ofthe connecting links requires' that each of them be arranged to handleall classes of calls, including local subscriber-tosubscriber calls,interexchange subscriber-to-subscriber calls, originated and receivedtoll calls, calls to single-party and multi-party lines, revertingcalls, calls from pay-station lines, and calls to a P. B. X (privatebranch exchange).

The invention is disclosed as embodied in a multi-exchange network ofcommunity automatic exchanges, including at least two communityautomatic exchanges interconnected with each other by two-way trunklines, one of the community automatic exchanges (termed the tandemexchange)` being interconnected by two-way trunk lines with each of twomanual exchanges.

In the parent application, the invention is further illustrated asapplied to a switching arrange ment wherein the connections are set upin a community automatic exchange through the medium of any one of anumber of finder-con nector links, each such link including relayswitching mechanism comprising a finder having access to all the linesof the exchange, and other relayA switching mechanism comprising aconnector having access to all the lines of the exchange. Y 1 u Thedrawings The accompanying drawings, comprising Figs. 1 to 3, show as'uicient amount of the equipment in a telephone system embodying thefeatures of the invention to enable the invention to be understood:

Fig. 1 shows the paths taken by the trunk lines interconnectingexchanges of the system;

Fig. 2 is a'diagram showing the scheme of the arrangement in theexchanges of Fig. 1; and

Fig. 3 shows the circuit arrangements of a twoway repeater in aterminating exchange of the system.

The system As shown in Fig. '1, the system includes a pair l of manualexchanges A and B and a pair of automatic exchanges C and D. Theexchanges C and D are community automatic exchanges, each arranged toserve a separate community.

As indicated in Fig. 1, the community automatic exchanges C and D areinterconnected by a D in the illustrated example responsive to therdialing of the digit 0.

Similarly, it is indicated that there are seven two-way trunk linesinterconnecting exchanges A and C, reached in exchange C responsive tothe dialing of the digit 0, and that there are lve twoway trunk linesinterconnecting exchanges B and C, reached inthe exchange C responsiveto the dialingof the digit 9.

The arrangement illustrated in Fig. 1 is further 3 intended to indicatethat an operator at exchange A can extend connection to exchange Bthrough the tandem automatic exchange C by taking an A-to-C trunk linefor use and dialing the digit 9, while an operator at exchange B cansimilarly extend connection to exchange A by taking a B-to-C trunk linefor use and dialing the digit 01- Fig. 1 is further intended to indicatethat a subscriber of the terminating exchange D can reach manualexchange A by dialing the digits 0 and 0, and can reach the manualexchange B by dialingl the .digits (l and 9.

Referring now to Fig. 2, comprising parts l to 3,

the manual exchanges A and B of Fig. 1 are indicated by rectangles inthe up-perleft-hand corner of part l; the tandem community automaticexchange C is represented by the rectangle covering a portion of part 1and a portion of part 2; and the terminating community automaticexchange D is represented by the rectangle in part 3 of Fig. 2. Y

Manual exchange A The equipment in exchange A includes the jack J l,illustrative of the jacks through which the subscriber lines of exchangeA are reached; the jack J 2, illustrative of the jacks through whichtoll lines connected with exchange A arereached; the cord circuit CCI,and the jacks J3 to J5 which are three of the seven jacksrepresentingthe manual-exchange terminalsof the seven associated interexchange trunklines, of which trunk lines A-TI, A-T2, and A-T'! are inclicated'inFig.2. Y

The equipment in the manual exchange A further includes a trunk circuitinterposed between l each of the two-way interexchangetrunk lines andthe corresponding Switchboard jack. The trunk circuits for the indicatedtrunk4 lines are respectively A-TCI, A--TC2, and A-TCL Manual exchange BSimilarly, the equipment in exchange B includes the subscriber-'linejack JS, cord circuit CCZ, trunk jacks Jl to J9, and trunk circuitsB--TCI, B-TC2, and B-TCE.

Tandem automatic archange C' .As previously noted Yeach of the communityautomatic exchanges includes finder-connector links eachhaving a fullcapacity of two hundred tending horizontally below the rectanglesindicating the nders and connectors. These twenty horizontal lines thusindicate the full number of tWo hundred line multiples.- e

The tens subgroups of line multiples are sometimes referred to as levelsUsing this expression, each of the finders and connectors has twentylevels of contacts (ten sets of contacts to a level) and each of theshort heavy horizontal lines below a iinder or connector represents aseparate one of such levels of contacts. In the relay type of switchingmechanism illustrated in the parent application, each such level isrepresented by a separate gang relay carrying ten sets 0f c ontacts.

The upper set of levels of the nders and connectors comprises the rsthundreds group and this hundreds group is reached as previously notedwhen either of thev hundreds'digits 2 and 3 is dialed. The lower set oflevels comprises the second hundreds group, which, as previously noted,is reached when either of the hundreds digits 4 and 5 is dialed. The tenlevels in each hundreds group have the tens digits 1 to 9 and 0 assignedrespectively thereto, as is indicated below the nder FI and below theconnector Cl.

Each .of the line multiples has a line circuit connected thereto. Theline circuits LC-ZII, LC-2'l2, and LC-fl l, for example, are connected crespectively with line multiples #2| i, #2l2, and

#211, being line multiples l, 2, and 'l in the first level ci theuppermost hundreds group of the iinders and connectors. All of theseline circuits are identical, and each of them has a pair of individualmarkr conductors (a tens conductor and a units conductor). These markconductors are indicated schematically in Fig. 2 by the short linesextending to the left from the bottom of the rectangles indicative o thelineL circuits. As indi- 1 cated by the bracket and by the lineextending therefrom to the distributor DR, such mark conductors extendto the distributor, and control the distributor so as to cause thecurrently allotted finder to beset on the individual multiple associatedwith the currently calling line.

The uppermost or il level of the 2 hundreds group of'line multiples (theupper onein Fig; 2); in exchange IC has line circuits LC-DI to LC-associated respectively with the ten multiples thereof, of which linecircuits LC--20l to LC-23 are shown. The 'rst multiple in this tensgroup is illustrated as serving the twenty-party line #2tlg Sill. Thatvis, the same line is reached responsive to the calling of either 251er3l! i; When fully equipped, this party line has ten substations #Zillito #ZEHU and" ten substations #301 lto #30ML a total of twentysubstations. For convenience of illustration, only the first, second andlast substation in eachV tens group on the twenty-party line are shown.l v

Y Line #282, associated with the correspondingly numbered line multipleand with line circuit LCV-202, is illustrated as a four-party line, suchas may be used for residential party-line service within the town orvillage. The directory num-Y bers of thesubstations on four-party line#282 may be #2921. to #2024; y

l, Line multiple #203, associated with line circuit LQ- -20 3; isillustrated as serving pay-station line #293; havingA pay station #203|thereon (the party digit l being added to the line designation of eachrindividual line to makeV the directory numbers uniform in the number ofcontained digits) .s p

The other line multiples of the above tens group may be arranged toserve either party lines or individual lines, and any station may or maynot be a pay station, as desired. The same is true of the line multiplesinthe other tens groups.

rIhe E level in thefZ hundreds group is illus- I trated as associatedwithten P. B. X lines #25| to #258, extending to P. B. X #25! l. Theconcerned 'multiples are Aassociated respectively with linecir-cuitss'uch as LCI-25|, IrC- 252, and LC 250.

As will be hereinafter described,` the arrangement is such thatv theiirst P. B. X line #25! is taken for use if idle, when the E. B. Xdirectory number 2511 is. called. Ii the rst line isvb'usy,

. the first idle one of the subsequent lines is 'taken for use and thecall is completed thereover, the connection being denied and the busysignal returned only in case all P. B. X lines are in use. On the otherhand, if the number of any line in the P. B. X group other than that ofthe rst line is called, connection is completed to the particular linecalled, if it is idle, but the connection is denied and a busy signal isreturned if that line is busy.

It is to be noted that the levels I, 2, and 3 of the 2 hundreds group inaddition to the respective level designations, have the designations(9), and (S) respectively applied thereto below the connectors. This isintended to indicate that, when the digit in parenthesis is called as arst digit, the connector in use operates as a single-digit connector tomake connection with the first idle interexchange trunk line served bythe level to which the dialed single-digit number is assigned. Forexample, it was pointed out in connection with Fig. l that the dialingof the single-digit number 0 in exchange C .results in the extension ofconnection from exchange C to exchange A over an idle one of the seventwoway interexchange trunk lines between exchanges A and C. These seventrunk lines are served by the iirst seven line multiples in the rstlevel of the 2 hundreds group in Fig. 2, these multiples havingassociated therewith line circuits such as LC-2I l, LC-Zi2, and LC-Zll.The illustrated ones (A-TI, A-T2, and A-T'I) of these seven trunk linesextend in exchange C respectively to the repeaters iR-I, 0R-2, and[iR-l. The switchboard side of such of the repeaters R-l to DR-l isconnected respectively with'the multiples associated with line circuitsLC-Zl l to LC-2I1.

Similarly, the dialing of the digit 9 in exchange C causes the connectorin use to extend connection by way of an idle one o f the rst fivemultiples in the second level of the 2 hundreds group, through one oranother of the repeaters such as 9R-l to .0R-5, and over a trunk linesuch as B-TI to B-TE, to exchange B.'

The dialing of the digit 8 in exchange C results in connection beingextended by the connector in use through anv idle one of the rst sixmultiples in the third level of the 2 hundreds group, through one oranother of the repeaterssuch as BR-I to 8R-6, and over one of the trunklines f C-Ti to C-T6, to exchange D.

One of the lines associated with the 4 hundreds group of line multiplesis shown. This is the twenty-party line #4l l; 5| I, associated withline circuit LC-dl I Iand the correspondingly numbered line multiple.This line may have ten substations #4i I! to #4I l0 thereon indexedbythe calling of the hundreds digit 4, and ten other substations #5l H to#5ml thereon indexed by the calling of the hundreds digit 5.

Terminating automatic exchange D The arrangement of finder connectorAlinks, line multiples, and line circuits in exchange D is similar tothat above described in exchange C". Connectors Ci to CX are illustratedas linked respectively by linksLl to LX withv the finders FI' to FX',such finders being controlled by the distributor DR.' under the controlofthe line circuits, such as LC2H, for example.

As indicated bythe designation (0) applied tothe rst level of the 2hundreds group in exchange'D', such level1is.use.d when thesingl'edigitnumber '0 is dialed,rto give access t th interexchange trunk lines C--TIto C-T6, byY

6i way ofthe repeaters RI to R6, the flrstsix line multiples in thislevel being used for this purpose.

With respect to each of the exchanges C and D, it will be understoodthat in any level assigned to interexchange trunk lines, any linemultiple not required for the interexchange trunk line group may be usedfor a subscriber line and called by the regular directory numberassigned according to the position occupied by the concerned multiple.This is illustrated by line #2 I1 of exchange D, serving individual-linesubstation #2|1I, connected to the seventh line multiple in the sametens subgroup serving the six interexchange trunk lines C-Tl to C-T6.

The other illustrated subscriber lines of exchange D are thetwenty-party line #20|; 30|,- and the pay-station line #202.

The circuit drawings DETAILED DESCRIPTION The system to which theinvention is applied having been described generally, a detaileddescription of the operation of the system will now be given, so far asit directly concerns apparatus shown in Fig. 3.

A. Local calls from tandem exchange C to terminatz'ng exchange D Thehandling of local calls from subscriber lines to tandem exchange C tolines of terminating exchange D will now be described. For this purpose,it may be assumed that a subscriber at pay station #203| (Fig. 2, part2) desires to converse with the subscriber at substation #20| 2 on partyline #201; 30| of exchange D (FigLZ,

x part 3).

It may be assumed that, when the receiver is removed at the calling paystation, operations occur as described in the parent application toextend the connection from the calling line through the nder FI of Fig.2, part l, to the connector Cl of Fig. 2, part 2, whereupon the seizedconnector CI is prepared for operation as explained in the parentapplication.

Since the calling subscriber is calling a line of another exchange, hefirst dials the singledigit number assigned to such other exchange (thedigit 8 in the assumed example), after which he waits for dial-tone fromthe called exchange before calling the number (2012) of the desiredsubscriber in the called exchange.

When the digit 8 is dialed into the seized connector CI as the initialdigit, operations occur as described in the parent application to causethe connector to be set upon as idle one of the trunk lines (C-TI toC-TG) interconnecting exchanges C and D. When this occurs, theconnectorfswitches through to extend the line multiple of the callingline directly to the local switchboard conductors extending to therepeater (BR-I to (iR-6) associated with the idle trunk line. It may beassumed that the trunk line C-I'i is seized, by way of repeater 8R|.Thereupon, operations occur as described in the parent application tocause the conductorsl comprising trunk C-"I"I to be 'bridged in therepeaterl-BR-SI of the calling exchange C,

A1. Preparing repeater R1 4for incoming operation In exchange D, retardcoil 60 Vis connected between ground and the tip conductor Aof trunkline C-Tl, through contacts 625 andthe upper left-hand Winding "ofrepeating coil BBB, While incoming line relay B05 is connected betweenthe free pole of the exchange battery and the ring conductor of thetrunk line, through contacts B26 andthe lower left-hand repeatingcoilwinding. AsY a result, line relay 605 operates over the trunk line C-@Tlwhen it is bridged as described in the repeater BRf-. ln'comin'g releaserelay SES next operates through contacts Vof line relay 505, andoperates incoming transfer relay BIB.

Diierential detector relay i503, whose windings are connected in seriesrespectively With retard coil vlill! vand incoming line relay tii.is'not oper ated at this time because the current flow is balanced inits two windings. Detector relay Vt03 is not operated at any time duringa call of the class under consideration because of the operatedcondition of'detector relay 553 in repeater SR-l which maintains itscontacts 'open to avoid an unbalancing of the interexchange irunl-lineconductors at lthe end of each dialing operation, as will be explainedhereinafter.

A2. Bridging talking conductors of the 'line multiple At armatures i527and 528,.'l'nco1ning transfer relay 6 I6 disconnects retard coil i2 andoutgoing line relay SIS, and subs.itutes a bridge across the tip andring conductors of the associated line multiple #211. bridge may betraced from the front contact of armature 621, through the uppercontacts of incoming line relay G65, the low-resistance lett-handWinding of polarized relay GGS, and resistor 633, to the front contactof armature 628.

A3. Seieing a connector in 'each'ange D In line circuit LC-2H, linerelay 622 now operates over the bridge established in repeater Rl, andapplies ground potential to the associated T and U marking conductors soas to cause the distributor DR-l (Fig. 2, part 3) tocperate an idle oneof the associated finders to link a connector with the associatedcalling line multiple #211. It may be assumed that the finder Fi is idleand is accordingly operated. by the distributor DR to link the connectorCi" with the calling line multiple #2l l through the finder-connectorlink Ll. This operation is as described in the parent applicationin'con'nection with the corresponding apparatus of exchange C shown inFigs. 11 to'l3 therein.

, When the connector Cl has been taken `for use and prepared foroperation, it returns a dialtone signal over the established connectionas eX- planed in the parent application for the connector Ci of Fig. 13therein. Upon hearing the dial-tone signal, the calling subscriber atpay station #253i (Fig. 1G) in exchange C dials the digits 2, 0, 1, and2 in the desired exchange-D number.

Alle. Repeating the digit impulses from exchange CV to exchange .D

Each time a digit of the desired numberris called, the liner'elay (notshown herein) of-re-f 8 peater SRI (Fig. 2) is 'restored momentarily av'corresponding Inu'm'ber of times. Upon Veach such `'rhoinentar'yrestoration, the previously noted bridge across 'the conductors ofVtrunk: lirico-Tl is opened. producing a momentary restoration ofincoming line relay 'E05 of the repeater Rl.

In fthe repeater Rl, upon the first restoration of incoming ln'e relay605 of any series, a circuit is closed through contacts ofslow-restoring release relay 686 for slow-restoring series relay 601.Relay7 G01 'accordingly operates and remains operated throughout theseries of impulses. At the upper contacts ofse'ries Arelay S0?, resistor602 is shunted around resistor 633 and the leftehand winding of relay609 to improve the iinpulsing c'iicuit to the connector in use.

Upon each-momentary restoration of line relay B95, the bridge Yacrossthe conductors 'of the associated line multiple #2H are opened at theupper contacts thereof, thus effectively repeating the dialed impulsesto the connector Cl (Fig. 2, part 3).

A5. Completing the connection oy local-con- Inector operation inexchange D The connector Cl responds (as hereinbefore described for theconnector Cl, Fig. 13) to the digits .repeated thereto at the repeaterRl to complete connection to the called subsation #2N2 on yparty line#20h 30|. Assuming that this lline is idle, the connection is made andringing current is applied. In the call under consideration, detectorrelay 603 of repeater vRl not having operated, s1eeve-con'.rol relayi302 isconsequently not operated, and no ground potential therefore isapplied by repeater RI to the sleeve conductor of the associatedmultiple #2i I. As a result, the connector in use (connector Cl', Fig.2, parl'I 3) changes over from toll operation to local operation, asdescribed in the parent application, for the connector Cl, Fig. 13therein.

A6. Answered supervision Y When the called subscriber answers, connectorCI operates' to cause the current flow to be r'eversed over its incomingconductors, whereby the current v110W.` in the tip and ring conductorsof liii'e multiple #Zltassociated With the repeater Ri is reversed. Whenthis occurs, polarized supervisory relay E09 in the repeater Rioperates', whereupon incoming supervisory relay Gti is operated throughcontacts of incoming transfer re'- lay fili!Y to reverse the conductorsof the trunk line C-TL I y InA repeater' 8R-|, the polarized supervisoryrelay (not shown herein) now operates to cause reversal of Ythe tip andring conductors of the associated line multiple #23I. The current new inthe calling payestation line of Fig. 1i) is there` by reversed,rendering the pay-station instrument inoperative, as described in theparent application, until the subscriber deposits the requisite coin tothereby again render it operative for conversational purposes.

A7. Disconnect supervision I`f ythe called subscriber replaces hisreceiver rst, the current flow is reversed back to normal direction inthe connector in use in exchange B, whereupon relays '609 and 60,1' inrepeater Rl restore, causing the" repeater 8R-l to reverse thecurrentovf in the callingline back to normal drection.

- A8. Clearing oatg When the receiver is replaced at the callingsubstation, the established connection clears out as will now beexplained.

The line relay (not shown) of repeater SR-l restores when the receiveris replaced at the calling substation. It cpen-circuits and restores thedistant line relay Bilt, at the same time initiating the restoration ofrelay 06.

The remaining portion of the connection, including the connector in use,is cleared out as hereinbefore described in connection with theconnector Cl (Fig. 13). When this occurs, cutoff and lockout relays 624and $23 of line circuit LC2 l l restore, returning .the line circuit toits `illustrated normal condition.

B. Manual-exchange calls through tandem exchange C to terminatingexchange D The handling of manual-exchange through tandem exchange C tolines of terminating exchange D will now be described. For this purpose,itmay be assumed that the operator at exchange A receives a call for asubscriber of terminating exchange D. It may be assumed that the trunkline A-Tl (Figs. 7 and 8) associated vwith trunk circuit A--TCi andrepeater R-l, is

used for this call.

B1. Seieing and preparing a connector in tandem exchange C When acord-circuit plug is inserted into the jack J3 (Fig. 7), operations asdescribed in the parent application occur, causing a nder in exchange Cto connect with the calling trunk line A-Tl. It may be assumed thatinder FI of Fig. 11 responds at this time to extend the call over theassociated link L! to the Connector Cl. The

`connector Ci is thereupon prepared for operation as described in theparent application, andreturns a dial-tone signal to the calling manualexchange.

B2. Dialing the single-digit number of emchanye The calling operator nowdials the digit .8 assigned to the terminating exchange, causing theconnector C! to be operated to take an idle one of the concerned trunklines for use as described in the parent application.

B3. Seieing repeater 8R-1 It may be assumed that the trunk line C--Ti is.idle and allotted at this time, in which case the connection isextended through line multiple #23| to the repeater R-L B4. Preparingrepeater fR-1 for outgoing tollL operation rEhe seized repeater SR-l isvnow pre-pared for outgoing toll 4operation as explained in the parentapplication, and. is thereby prepa-red to condition calls repeater RIsubsequently for toll operation, as will be describedhereinafter.

B5. Preparing repeater R1 for incoming operation B6. Repeating the digitimpulses through tandem exchange C to terminating exchange D Asexplained in the parent application, the impulse series constituting thedigits in the desired number are repeated, through repeaters ilR- I and8R|` to line relay 605 of the repeater Rl, which in turn repeats `themat its upper contacts to the connector in use in exchange D.

B7. Relaging the grounded-sleeve, toll-call indi'- cation from exchangeC' to exchange D As explained in the parent application, with repeater8R-l conditioned for toll operation, it momentarily unbalances thecurrent iiow in the conductors of trunk line C-Tl at the end of eachdigit series, thus unbalancing the current flow in the two windings ofdifferential-detector relay 603. i

B'la. Conditioning repeater R1V for toll operation In the exchange D,detector relay't of re.- peater Rl now operates to close a circuit forsleeve-control relay 302 from ground on the sleeve conductor of theassociated line'multiple #ZIL through 'the inner upper contacts of theoperated incoming transfer relay 6H? and contacts of detector relay 603.Sleeve-control relay 602 now operates. itself to the associated sleeveconductor, independent of the contacts of detector relay B3.

At its lower contacts, relay 692 completes a ground connection to thesleeve conductor of the associated line multiple #2 l I as follows: fromground through the inner lower contacts of the operated incoming releaserelay 606, through the lower contacts of sleeve-control relay E, theupper contacts of relay 602, and through contacts of relay Gill to thesaid sleeve conductor. The ground potential is thus applied to thesleeve conductor of line multiple #2 Il to mark the call as one comingfrom a manual exchange. I

When the above-described temporaryunbalanced condition is terminated,detector relay 603 restores, but sleeve-control relay 602 remainsoperated thereafter through its own contacts independent of the contactsof detector relay etti,

The unbalancing operation is repeated atthe end of each dialed digit,but is of no particular eiisct after sleeve-control relay 602 hasoperated and locked as above noted.

B8. Conditioning the connector in use in exchange D for toll operationAs explained in the parentl application, vwhen the complete number hasbeen dialed and the connector in use in exchange D tests the called lineand operates either its busy relay or its At its upper'contacts, itlocksv operating at this time by the ground potential maintained on thesleeve conductor of the connection in exchange D by the above-mentionedground connection to the sleeve conductor S of the calling line multiple#2H associated with the repeater RI. Accordingly, the connector in usein exchange D is conditioned for toll operation by the failure of theabove-mentioned detector relay to operate.

B9. Answered supervision are reversed when the called subscriberreplaces his receiver. The called subscriber can, of course, signal theoperator by manipulating his hookswitch as desired, the hookswitchsignaling being repeated from repeater RI to repeater BR-I, and from therepeater BR-I to the repeater IBR-I, and from the repeater IIR-I to thetrunk circuit A-TC I B11. Clearing out When the operatorat exchange Aremoves her plug from the jack J3, the resulting open-circuit conditionis relayed by the repeater BRFI to the repeater 8R--I, thereby to therepeater RI, and thereby to connector in use in the ter-A minatingexchange D. The connection in tandem exchange A is cleared outresponsive to the removal of ground potential from the sleeve conductorof line multiple #2H associated with repeater DR-I or to the removal ofground potential from the sleeve conductor of line multiple #23|associated with the repeater 8R-I, Whichever occurs last.

In the exchange D, the connector in use removes ground potential at onepoint from the sleeve lead of line multiple #2l I, Fig. 6, part 2, whenit clears out. Incoming release relay 66S of repeater RI restores as aresult of the deenergization of incoming line relay E05. When it doesso, it removes ground potential at one point from the sleeve conductorof the associated line multiple #ZI I. Responsive to whichever of theseoperations occurs last, line circuit LC-2I I clears out, and relays 602and E I 0 restore.

C. Local call from terminating echange D to tandem echange C The way inwhich subscribers of terminating exchange D are given service on callsto subscriber lines ofr tandem exchange C will now be described. Forthis purpose, it may be assumed that a subscriber at pay station #202i(Fig. 2, part 2) on. line #202 of exchange D desires to converse with asubscriber of tandem exchange C.

C1. seizing a connector in exchange D When the receiver is removed atthe calling pay station, a finder such as FI (Fig. 2, part 3) is causedto operate to link a connector such 'as CI' with the calling line,whereupon such connector is prepared for operation and a dial-tonesignal is given to the calling subscriber.

l2 C2. Dialing the single-digit number of exchange C The callingsubscriber may now dial the digit 0 assigned to tandem exchange C fromthe standpoint of terminating exchange D, with the result that theconnector in use is operated as hereinbefore described for connector CI(Fig. 13) to make connection with an idle one of the trunk linesinterconnecting exchanges C and D. It may be assumed that the trunk lineC-TI interconnecting the repeaters BR-I and RI of Figs. 5 and 6 is idleand allotted at this time, in which case it is taken' for use by Way ofline multiple L. M. #2| I (Fig. 6, part 2).

C3. Clearing the line circuit LC-211 When the connector in use inexchange D seizes line multiple #2| I therein, associated with repeaterRI, Fig. 6, it thereby extends the conductors of the calling line to thetip and ring conductors T and R. of the seized line multiple, andextends the still-grounded sleeve conductor of the connection to thesleeve conductor S of the line multiple. Cutoi and lockout relays 624and 623 are thereupon operated over the associated sleeve conductors toclear the line circuit LC-2I I'.

C4. Preparing repeater R1 for outgoing operation In the repeater RI,retard coil 6I2 is normally connected between the free pole of theexchange battery and the ring conductor of the associated line multiplethrough contacts B28 of incoming transfer relay 6 I Il and the lowerleft-hand Winding of repeating coil 600, while outgoing line relay 6I3is normally connected between ground and the tip conductor of the linemultiple through contacts 621 and the upper right-hand winding of therepeating coil. Consequently, outgoing line relay EIS is energized overthe calling line when the associated line multiple #2H is seized. RelayBIS thereupon operates causing the successive operation of outgoingrelease relay III and outgoing transfer relay 608. Outgoing transferrelay 608 applies a holding ground potential to the sleeve conductor ofthe associated line multiple as follows: from ground, through normallyclosed contacts controlled by inner armature of release-timer relay 6I5,the lower Winding of transformer GIG, and through the inner uppercontacts of outgoing transfer relay 608, to the associated sleeveconductor.

With outgoing release relay 6I I operated, classtone relay SI1 operatesthrough contacts of outgoing supervisory-control relay 6I4, followed bythe operation of class-tone relay 6I8, to prepare for the giving of aclass-tone signal when the call is answered, which signal is importantonly when a manual exchange is being called.

At armatures 625 and 62B, outgoing transfer relay S08 disconnects theconductors of trunk line C-TI from retard coil E02 and incoming linerelay 605 and transfers them to a bridge controlled by the uppercontacts of outgoing line relay GI3. This bridge may be traced from thefront contact of armature 625, through the upper contacts of outgoingline relay 6I3, the low resistance left-hand winding of polarizedsupervsory relay 609, and through resistor 633, to the front contact ofarmature 626.

C5. Seieing a connector in exchange C Responsive to the closure of theabove-traced bridge across the conductors of trunk line C-TI, therepeater 8R-I in exchange C operates as described in the parentapplication to cause an lay 6.2i! operates connection. Such 'connectoris thereby prepared for operation. c

The usual dial-tone signal is sent back by the seized connector inexchange C through the repeaters BR-I and yRI to the calling line interminating exchange D to inform the calling paystation subscriber thathe Vmay now dial the `directory number of the desired subscriber in thecalled tandem exchange C.

C6. Repeating the digit impulses Upon dialing of each of the four digitsin the directory number of the called line in exchange C, outgoing linerelay 6I3 of repeater RI is momentarily restored a number of Vtimescorresponding to the value of the digit. Each time it restores, it opensthe above-traced bridge across the conductors of trunk line C--TI at itsupper contacts, whereby the calling-device impulses Vare repeated to theseized connector by way of repeater 8R-I, causing such connector tooperate as described in the parent application to set up the desiredconnection.

In the repeater RI, each momentary restoration of outgoing line relay6I'3 closes acircuit for series relay 601 through contacts of Ioutgoingsupervisory relay 5I4 and contacts of the operated outgoing releaserelay 5I I. Relay 601 accordingly operates and remains operatedthroughout -the seriesof impulses. it shunts resistor At its' innerupper contacts, 63| around the winding of retard coil 6I2 to improve theresponse of line relay 6I3, while at its upper contacts it shuntsresistor 632 across resistor 633 and the left-hand winding of relay 609,to kimprove the response `of incoming line relay 5I4 of the repeater8R-I.

, C7. Counting the number of digits to determine destination of .thecall Arrangements are provided in the repeater RI to count the number ordigits dialed by a calling exchange-D subscriber after seizure of therepeater to determine thereby whether the call is being made to one ofthe manual exchanges (in which case only a single digit, 9 or 0 isdialed) or is for a local line of exchange C (in which case four digitsare dialed). The purpose of the determination is to enable reverselbattery supervision received by the repeater RI when the callisanswered to be relayed back to the calling line if Ythe call is to asubscriber line of exchange C, but to be withheld in the repeater RI ifthe call is to one of the manual exchanges, whereby .calling pay-stationsubscribers of exchange D are permitted to make free calls to thevmanual exchanges, but are required to deposit a coin before-beingpermitted to converse with called subscribers" of exchange C.

C7a. Disconnecting the outgoing supervisoryie- `Zay when the vfirstdigit is counted cuit or the lowerwinding of digit-counter'relay 820, asfollows: `from ground through the .inner lower contacts of the operatedoutgoing release relay 6I I, lower armature and front contact ofseries-relay 60T, upper armature and back contact of digit-counter relay6 I 9, and thence to battery through the lower winding of relay 62.0.Re-

When this. circuit is closed.

vits lower contacts,

.ates therein. Upon -6I9 however, Y'lower contacts and .upper winding. Y

visory relay $2 I so as toprevent therelaying back of reverse batterysupervision unless relay .62.5 is subsequently restored. At its uppercontacts.

relay'SZ prepares a restoring circuit for its upper,

winding, and at its inner lower contactsit closes aseli-locking circuit,as follows: from ground through the lower contacts `of relay SII, YtheVinner lower contacts of relay 6253, the lower winding of relay 6I9, andthrough the :lower winding of relay 1629 to battery. The lower windingof relay 619 is not energized in this locking circuit for the timebeing, for it is short-circuited by the initial circuit closed for thelower winding of relay 625.

When slow-restoring series relay 661 falls back at the end of the firstdigit dialed following the 'seizure ofthe repeater R, it opens theinitial circuit above traced for the lower winding lof relay 620. Relay'62E remains operated .in its above traced locking `circuit and relay6I9 operoperating, relay 6I!) closes a locking circuit for through theinner lower contacts of release relay GI I, whereby it is maintainedoperated independent of the contacts of relay $20 until the connectionis cleared out.

At its upper armature, relay SIS opens a further `point in thepreviously established initial circuit for .the lower winding of relay620 and prepares arestoring circuit for the upper winding -of relay 62e.

On calls to the manual exchange, the single digit dialed after theseizure of the repeater RY t -suiii'ces to fully extend the connection,Vand relay 620 is, therefore, not restored by further dialing. On suchcalls, outgoing supervisory relay i52| remains disconnected. In thepresent example, however, `the call is for a' subscriber line of thetandem exchange and three additional digits are dialed, vcausing relay628 to restore, as will be described, to again connect up outgoingsupervisory relay 62|.

C712. Reconnecting the supervisory 'relay when more than one digit iscounted When the second digit in the desired number is dialed, seriesrelay 661 is again operated and remains operated throughout the digit.At its lower armature and front contact, it closes a eircuit through theinner contacts of the operated relays SIS and 620 for the upper windingof relay 6,20. Relay 625 is a diiierential relay, as indicated. As aresult, relay E20 is deenergized by the cur:- rent flow in its v.upperwinding, and it accordingly restores. Upon restoring, relay 525i againconnects up outgoing supervisory relay 5,2! at its lower contacts; itdisconnects its upper winding at its upper contacts; and at its innerlower contacts, it .opens the locking circuit through the Vlowerwindings of relays EIS and y62). Relay remains operated through its .own

With relay 6I 9 locked operated, and with relay 625 again restored,these relays are not affected by the further oper-ations of series relay60'! during-the dialing of the remaining 'two digits in the number.

C8. Answered supervision When the called subscriber responds, the`connector `in use in exchange C reverses the current flow -to repeater8R-I, which thereupon reverses the conductors of trunk line C-Ti,reversing the current flow through the left-hand winding of.polarizedrelay in :the repeater RI. Relay B09 it Lu-iscormeas outgoingeimer-9 its upper winding, to ground thereupon operates its armature,650, closing a .required to deposit a coin to recondition the paystation for conversation.

C9. Disconnect supervision Assuming that the called subscriber is thefirst to replace his receiver after conversation, the

above described supervisory operations are reversed, returning thecurrent flow in the calling line in exchange D to normal direction.

C10. Clearing out When the receiver is replaced at the callingsubstation, the resulting open-circuit condition is relayed by repeaterRI of Fig. 6 to repeater BR--L and thence to the connector in use inexchange C, permitting such repeater and connector to clear out asdescribed in the parent application.

In the calling exchange D, outgoing release relay 6H restores a slightinterval after the restoration ci outgoing line relay 6|3. At its innercontacts, relay 6H open-circuits and restores outgoing transfer relay633 and digitcounter 'relay BIS. Outgoing transfer relay 633, at itsinner contacts, removes ground potential from the associated sleeveconductor, thereby permitting the line circuit LC-2|| to clear out alongwith the connector in use and the calling line circuit. Series relay 601is operated momentarily upon the restoration of line relay 6|2 butclears out responsive to the restoration oi release relay B|| withoutproducing any particular result at this time.

D. Handling calls from terminating exchange D to manual exchanges A andB The handling of calls from terminating exchange D, through tandemexchange C, to manual exchanges A and B will now be described. For thispurpose, it may be assumed that a subscriber at pay station #202| (Fig.2, part 3) desires to make a call to or through one of the manualexchanges A and B, manual exchange A, for example. Y

D1. Calling tandem exchange C When the receiver is removed at paystation #2ML an idle one of the connectors Cl' to CX is linked to thecalling line #202 by operation of the associated one of the finders Fl'to FX' under the control of the distributor DR as hereinbeforedescribed. Such connector thereupon returns a dial-tone signal to thecalling pay station line, and it responds to the digit 0, when dialed,to extend connection to tandem exchange C over an idle one of theinterexchange trunk linesC-TI to C-T6. It may be assumed that trunk lineC-TI is idle and allotted at this time and is therefore seized, by wayof repeater RI of Figs. 2 and 6.

When the repeater Rl is seized in the terminating exchange D, it isypreparedior outgoing operation' as hereinbefore described, its relay6l3,6||,688,6|1,and 6|8 operating.

The repeater 8R-I in exchange C is now prepared for operation responsive`to the bridging of lthe associated' :trunk line C--Tl in the repeaterRI as hereinbefore described.

An idle connector in tandem exchange C is now linked to the associatedline multiple #23| by iinder operation. It may be assumed that theiinder Fl operates to link the connector Cl to the calling multiple#231. The connector CI is thereupon prepared for operation.

D2. Calling manual exchange A f When the calling subscriber in exchangeD, on

Yhearing thev dial-tone signal now sent back from the connector CI inexchange C, dials the digit D assigned to the manual exchange A from thestandpoint of exchange C, the ten momentary interruption impulsesconstituting such digit are repeated by the repeater Rl of Fig. 6 to the.repeater 8R-l, and are thereat repeated to the seized' connector CI. Asa result, the connector Cl operates as described in the parentapplication to cause connection to be made with the called manualexchange A, by way of the trunk line A-TI for example. This connectionis made by way of line multiple #2H and the repeater OBf-l.

As explained in the parent application, ringing current is now sentmomentarily over the trunk line A--TI to signal the operator in exchangeA.

D3; Answered supervision When the operatorin the called manual exchangeA answers a call, operations occur, as described in the parentapplication, in repeaters R-l and R-I to reverse the direction ofcurrent flow over the trunk line C-Tl, to relay answered supervision tothe repeater RI in exchange D,

In the repeater RI polarized supervisory relay 509 now responds andoperates outgoing supervisory-control relay 6 4.

D3a. Barring current reversal at repeater R Outgoing supervisory relay62| is not operated at this time because it is maintained disconnectedat the lower contacts of the operated digitcounter relay 62D, relay 620not having been restored in the present call, because only a singledigit was dialed, following the seizure of the repeater Rl, to extendconnection to the called manual exchange. The current flow is,therefore, not reversed in the calling pay-station line,

wherefore the calling pay-station subscriber is able to carry o-n aconversation with the operator in the manual exchange without vfirstdepositing a coin, as he is obliged to do before conversing when asubscriber of either of the automatic exchanges is called.

Upon operating as above noted,V outgoing supervisory-control relay 6Mdisconnects series relay 60'! at its middle lower contacts; at its uppercon- Vtacts, it closes a parallel bridge across the conductors of truckline C-TI including the 30,()00- l ohm right-hand Winding of polarizedsupervisory relay 60B, for a Vpurpose to be subsequently brought out;and at the back contact of its inner lower armature, it disconnectsclass-tone relay SI1.

D31). Class-tone signaling at repeater R1 Class-tone relays 6|1 and Sl,both of which are slow-restoring relays as indicated, now restoresuccessively. During the time required for outgoing release relay 5I I.

t3 idleffnder; tohlinkdts asscciatedauonnectontthe connection.Such-connectors-isgthereby:prepared for; operation.

The; usual dial-toneV signal iszfsentfback-xbiy'fthey seized; connector1in exchange C p'throughz the ref. peaters sRf-I and RI tothecallinglinezinfterminatingfexchangeD to .inform the:.ca1lmg paystationsubscriber that he mayfnow: dial'- the di rectoryfnumber.- of thedesired subscriber.- in'athe called ta ndern: exchange C;

C6. Repeating the digit.. impulsen Upon dialingg of each.. ofthe. four;`digits in the directory number of the called line in exchange C,-outgoingjlinerelay of repeaterRI 1 isLmoup the-desired connection.` l

In the repeater RI, each-momentary restora- 'f tion-offoutgoingflinerelay 3 I'3Y closest-a circuit lfor series relay GDI- through contactsof outgoing supervisory relay 5 I dandlcontacts of the operated Relayl601 accordingly operatesV and remainsoperated throughoutf the seriesofVv impulses.A At its innerupper= contacts; it shunts'- resistor 631aroundfthe winding offre;- tard coil 61.2, to-.-. improve.` theiresponse of line relay 6l3, while at its upper contacts, it shuntsresism-eszacross resistor ess-end-theflefnhand winding ofrelay; 609;V toimprovethgef response of` incoming linerelayf5 I 4ofthe repeater.' 8R;Ii

C7; Counting theznum'bere-of dyitsfto determine destination offtheccrliArrangements are provided. in the repeater R'I tol count the' numberof'digits dialed' by a calling exchangeeD'subscriber afterseizure of therepeater to determine thereby whether the call' is beingr made' to oneof thet` manual exchanges; (in whichcase only asingle digit,.9. or. 0,is. dialed) orv is. for.` a locali line.. of. exchange C; (in whichcaserfour. digits are dialed).` Thepurpose ofthe determination is to.enable reverse batterysuper.- vision receivedby the repeater RI. whenthecali isansweredto be relayedebacli to the callinggline if the c all is.to asubscriber line of. exchange C', butto be withheld inthe repeaterRI. ii?V the call is to one ofthemanualexchange, whereby callingpay-stationsubscribers` ofv exchangeA D. are

permitted to make fre e ..cal1sy to. the..man-ualSX.,-v

changes, but.` are. required to deposit, a, coin; be@ forebeingpermittedtoonyerse with; Aalle dgsubscribers.. of exchange C,

C'a. Disconnectz'ng the outgoing .supervi'so1y`- ree Zay whenthe'vvfirst dgitrisccounted The digit-counting oper-ation is'accomplished' by. digit-Counter relays- GIS and. $2.04 under. thecontrol of series relay 6.0.7

When relay 661 operates as, described in; ref

sponse to the irst repeated digit, incluses @Giltcuit for thelowerwinding ory digitvCounterVv relay 62B, as. follows:fromeround.-throughthe inner lower contacts of the operatedoutgoingrelease relay GII, lower armature and front contact of seriesrelay-S01, upper armature andback contact of'digit-counterrelay 6I 9;ahdthence-toabatteryv through the. lower winding oi?1 relay 62H1.. Reeflay 62 [L operatesy when: this.;circuiti.A iszclosedi. At

Suk

ISU

" inely. restores..

itsdowencontaots;.itndisconneetszouteoineesupsrr.

visoryirelayrglfso. astoprevent theerclayingfbanls ofi reverse;battery.v supervision; unless relayf tzt)l is; subsequently restored..At .its upper; cantante; relayf6-2 rpreparesza restoring; circuit forits upper winding; and; attitszinner; lower. contacts iii-closes`a;se1flo cking circuit, as follows: from ground through:` the;;1o.wer,-contacts;y oil relay 6H, the innersflower. contactsY of relay 62d, the;lower winding.: ofv relay BIS, and. through the lower windingzofxrelay 62 Il. to battery; The-lower wind: ing` ofrelay. 619 ispnotv energized inthis locking circuit for the timeibeing, for it vis shortfcircuited by;the.: initial circuit closed forI the; lower ,winding of relay 52B.

When slow-restoringseries relay 601 falls back at the end of`the firstdigit-dialedfollowing the seizure,of the; repeater., R, it. 0nenstl1e;initial circuit above traced for thelowei: winding of relay 620.. RelayS-Ztiremains voperated in. its above traced-locking: f ziruuit;y and,-relar; 6l 9.. open ates therein; T.T p o n operating,` relay -IScloses-a locking circuit for its upper winding, to ground through theinner lower contacts of release relayi! I whereby'itismaintainedoperatedindependent of the contacts of relay tti!y untiltheconnection' is cleared out.` l A-t its upper armature, relay Sie opens afurther point, in the circuit for; the lower winding` oflrelay S25 andprepares a restoring circuit for the upper'winding; of relayl tigt, v

@n. caus to the manualexehanee, the single digit.. dialed. after the..Seizurel Qf.- the repeater.; R sufoestofullr extend the Connectionransirela-r are is, tnereioize, not restored. by furtnerfdialing On. such.calls; outgoing, supervisory relay 6.2.! remains.) disconnected., Inthey present example, howeyerfthe'call is. for alsubscriber.- line 0fthe tandem exchange yand]y three additional; digitsare dialed', Causing.relay 629 tov restore, aswill. be d escribedttoagain connect up outgoingsuper-y visory rela-y;l 61|-,

717'.V Rec'onn-eetiny'4 the supervisory`l relay when morelthcmA one'digit is counted When the second digit in the desired number is dialed;series*` relay tlll'is again opera-ted'andremains operated throughoutthe digit. At its lower armature and iront contact: itcloses .a circuitthroughthe inner contacts of theoperated relaysIEI and 62.23 fortheupper windingof relay 622i., Rlfy 52 ..i s a. diierential relay, asindicated. Asa, resultLrelay 62e is deenergized by. 'the currentil'ow initsupper winding, andvit accord- Upon restoring). relay 625B. againconnects up outgoing supervisory relay 6' 2 I at its lower contacts; itdisconnects its upper winding at its vuppercontacts; and' at its'innerlower contact.S.it. opens the., locking cirllit through.. the lower..windings. 0.121 relays 613i.. andfZll; Relay .619, how'eyen, remains.Operated... throughits own lower contacts andupper. Winding. With relayiii-9-A lockedoperated, andwith rela-y E2G again, restored, these relaysare. notaiected by thev further operations of series relayr 5131iduring; thefdialing., of-v the remaining two dglSSfin the number.

C8, Answered supervision Whenthe called' subscriber responds, theconlnector in use: iny exchange C reverses the current flow.- to repeater3R- I which thereupon reverses the conductors of trunk line C-.TI,reversingrthe current., Hows' through the left-hand' winding ofpolarizedrelay 6092 in thelrepeater Ril. Belag/609 previouslyYestablished` initial y thereupon operates its armature S50, closing acircuit, through contacts of outgoing transfer relay 608, and contactsof the restored digitcounter relay 620, for outgoing supervisory relay62|. Relay 62| operates to reverse the current iiow over the tip andring conductors of the associated line multiple #2 i, thereby reversingcurrent iiow over the calling pay-station line #282 (Fig. 2, part 3).The calling pay-station #202| is thereupon disabled by the operation ofthe polarized pay-station magnet as described in the parent applicationin connection with pay station #203 The calling pay-station subscriberis thus required to deposit a coin to recondition the pay station forconversation.

C9. Disconnect supervision Assuming that the called subscriber is theiirst to replace his receiver after conversation, the

above described supervisory operations are reversed, returning thecurrent ow in the calling line in exchange D to normal direction.

C10. Clearing ont When the receiver is replaced at the calling nector toclear out as described in the parent application.

In the calling exchange D, outgoing release relay 6|! restores a slightinterval after the restoration of outgoing line relay 6|3. At its innercontacts, relay 6H open-circuits and restores outgoing transfer relayB33 and digitcounter relay EIS. Outgoing transfer relay 633, at itsinner contacts, removes ground potential from the associated sleeveconductor, thereby permitting the line circuit LC-ZH' to clear out alongwith the connector in use and the calling line circuit. Series relay68'! is operated momentarily upon the restoration of line relay 6|2 butclears out responsive to the restoration of release relay 6| I withoutproducing any particular result at this time.

D. Handling calls from terminating exchange D to manual exchanges A andBV D1. Calling tandem exchange C When the receiver is removed at paystation #2021, an idle one of the connectors Cl to CX' is linked to thecalling line #202 by operation of the associated one of the nders Fl toFX under the control of the distributor DR as hereinbefore described.Such connector thereupon returns a dial-tone signal to the calling paystation line, and it responds to the digit (i, when dialed, to extendconnection to tandem exchange C over an idle one of the interexchangetrunk lines .C-TI to C-T6. It may be assumed that trunk line C-TI isidle and allotted at this time and is therefore seized, by way ofrepeater RI of Figs. 2 and 6.

When the repeater Rl is seized in the terminating exchange D, it isprepared for outgoing operation as hereinbefore described, its relays6|3, 6| 508, SI1, and 6|8 operating.

The repeater BR-I in exchange C is now prepared for operation responsiveto the bridging of the associated trunk line C-Ti in the repeater R| ashereinbefore described.

An idle connector in tandem exchange C is now linked to the associatedline multiple #23| by nder operation. 1t may be assumed that the iinderFI operates to link the connector C| to the calling multiple #23|. Theconnector CI is thereupon prepared for operation.

D2. Calling manual echange A When the calling subscriber in exchange D,on hearing the dial-tone signal now sent back from the connector CI inexchange C, dials the digit 0 assigned to the manual exchange A from thestandpoint of exchange C, the ten momentary interruption impulsesconstituting such digit are repeated by the repeater Rl of Fig. 6 to therepeater 8R|, and are thereat repeated to the seized connector C|. As aresult, the connector CI operates as described in the parent applicationto cause connection to be made with the called manual exchange A, by wayof the trunk line A-Tl for example. This connection is made by way ofVline multiple #2H and the repeater R-L As explained in the parentapplication, ringing current is now sent momentarily over the trunk lineA-TI to signal the operator in exchange A.

D3. Answered supervision When the operator in the called manual exchangeA answers a call, operations occur, as described in the parentapplication, in repeaters UR-l and 8R| to reverse the direction ofcurrent now over the trunk line C-T|, to relay answered supervision tothe repeater Rl in exchange D.

In the repeater Ri, polarized supervisory relay 609 now responds andoperates outgoing supervisory-control relay 6 |4.

D3a. Barring current reversal ai repeater R1 Outgoing supervisory relay52! is not operated at this time because it is maintained disconnectedat the lower contacts of the operated digitccunter relay 620, relay 620not having been restored in the present call, because only a singledigit was dialed, following the seizure of the repeater R|, to extendconnection to the called manual exchange. The current flow is,therefore, not reversed in the calling pay-station line, wherefore thecalling pay-station subscriber is able to carry on a conversation withthe operator in the manual exchange without first depositing a coin, ashe is obliged to do before conversing when a subscriber of either of theautomatic exchanges is called.

Upon operating as abovenoted, outgoing supervisory-control relay 6|4disconnects series relay 60'! at its middle lower contacts; at its uppercontacts, it closes a parallel bridge across the conductors of truckline C-Tl including the 30,000- ohm right-hand winding of polarizedsupervisory relay 60S, for a purpose to be subsequently brought out; andat the back contact of its inner loger armature, it disconnectsclass-tone relay 6 D312.. Class-tone signaling at repeater R1 visor*-control relay 614.

i relay 618 to restore after relay 6Fl restores, the upper winding oftransformer 6MBl is bridged across the talking circuit in series withcondenser 630, to relay to the talking circuit any tone signal which maybe impressed on the sleeve conductor of the calling line. Such sleeveconductor is now extended, through the nder connector link in use to thesleeve conductor S of the associated line multiple #2 i l, and thisconductor is extended to ground through the lower winding of transformeriEi. The sleeve conductor of the line multiple associated with thecalling pay-station line #202 (Fig. 2, part 3) may have a class-toneconnection made thereto from a common classtone lead through anindividual condenser, as g illustrated in Fig. 10 of the parentapplication in connection with line multiple #293 associated with paystation #263i of tandem exchange The pay-station tone is thus receivedat the lower winding of transformer (316 and is induced in the upperwinding thereof and impressed across the conductors of the talkingcircuit through condenser 539 and the contacts of relays 5H and Sieduring the short interval in which relay 618 remains operated afterrelay 6l? restores. The pay-station tone signal is thus sent back overthe talking circuit to the called manual exchange to be heard by theanswering operator. The operator is thereby informed that the call a paystation.

The calling pay-station subscriber may now converse with the operator asdesired, not having to rst deposit a coin.

D4. Recalling the called manual-exchange operator it is disconnected atcontacts of outgoing supervi-` sory-control relay 6M, whereby thesetting of digit-counter relays El@ and B29 is not interfered with'.

Outgoing release relay 5H restores a short interval followingthe'restoration of outgoing line relay t i 3, but outgoingtransferre'lay il remains operated nevertheless, through the inner lowerarmature and front contact of outgoing super- As a result, outgoingtransfer relay E113 maintains the associated sleeve conductor groundedat its inner Lipper contacts to maintain the connection established inthel local exchange. At its upper contacts, line relay Elfi opens thepreviously traced low-resistance bridge across the conductors of trunkline C-Ti through the left-hand winding of polarized supervisory relay699, but relay 599 remains operated at this time in a high-resistancebridge including'both windings` of relay 69ain series,

and the upper contacts of outgoing supervisorycontrol relay 6M. Contacts59 are thereby maintained closed to maintain relay @i4 operated.

In the tandem exchange C, the above-noted substitution of ahigh-resistance holding bridge (in the repeater Rl) for the previouslyestablished low-resistance holding bridge, across the conductors oftrunk line C-Tl, causes the repeater 13R- to act similarly with resp-ectto its holding bridge for repeater iR-I. The latter repeater reversesthe existing current flow over the conductors of trunk line A Tl,causing the operators supervisory lamp (not shown) in the cord circuitto become lighted.

When the calling subscriber in exchange D- D5.V Clearing out When thecalling subscriber has replaced his receiver and the operaor has takendown the connection in the manual exchange, the entire connection iscleared out. The clearing out of the connection occurs in either of twoways, olependirig upon whether the operator disconnects first or thecalling subscriber replaces his receiver first. The more usual operationis for the calling' subscriber to replace his receiver first, and theclearing-out operations will be described under this assumption.

When the receiver is replaced at the calling substation, operations ashereinbefore described in connection with the temporary depression ofthe hoolrswitch contacts occur to cause the supervisory lamp to becomelightedin the manual exchange, being lighted steadily at this time as adisconnect signal. When the operator responds to the disconnect signal,by removing her plug from the jack J the repeater [iR- l responsivelyreverses current flow to repeater R-L which responsively reverses thecurrent line C-Ti to normal direction.

in the calling exchange D, 4polarized supervisory relay @e9 or"repeaterRl (which wasbeing,v held operated in a high-resistance bridgein-fj cluding both its windings and the upper `contacts of relay tid)restores whenthe current owover truni: vline C--Ti is reversed baci;l tonormaldirection `by the restoration lof incoming Vsupervisory relay 5l5. Upon restoring; relay (lopencircuits and restores outgoingsupervisory-control relay till. At the front contact of its ,innerylower armature, relay Sill open-circuits and restores digit-counterrelay li and outgoing transfer relay 55B. Relay silt thereuponungrounds' the associated sleeve lead at its inner upper contacts,

returning the repeater Rl and associated linev circuit LCM-2 l i tonormal condition and clearing out the portion ci the connection -inexchange D between the calling line and the Vrepeater Rl.

E. Permanentk at the repeater yR1 l RepeaterRl (Fig. 3i isprovided-'with releasetimer relay (il 5 and has associated therewithcornrnon start lead i356', corninon pickup lead PV', and common leadHi',

to the tirier T (Fig. i3, part' 5 of the parent applicaticn) in exchangelease relay ai i completes l a circuit connection at its lower armatureand front contact between The act of depressing the hoolrflow over trunkA associated with the two- Yn'iinute timer in terminating exchange Dsimilar terexchange trunk line 19 pickup lead Pl and the winding ofrelease-timer relay l'5.

If the call has not been answered, to thereby cause outgoing supervisoryrelay 614 to operate, before lead Pl is next grounded, release-timerrelay 615 operates over lead Pl and locks itself at its lower armatureto ground through contacts of series relay 6G? and the inner contacts ofoutgoing release relay 6i I.

If no dialing occurs during the next two-minute interval (to operateseries relay 651) and if the call is not answered during this interval(to operate outgoing supervisory-control relay BHI), relay M5 remainsoperated, and the associated sleeve conductor remains dependent upon thecontinued application of ground potential to the common hold lead Hl.Under this condition, when hold lead HI' is next ungrounded theassociated sleeve lead is consequently ungrounded, permitting theconnection to clear out and causing the calling line circuit to beplaced in lockout condition as described for other line circuits in theparent application.

The connection is similarly released following conversation (and theconsequent restoration of relay 5M) if theh calling subscriber does notreplace his receiver in the meantime.

F. Allotter control at repeater R1 The repeater Rl controls the #Iallotter relay in the associated trunk allotter over the allotterconductors 611i as explained in the parent application in connectionwith the repeater GRP-l and trunk allotter TA-lL When the repeater Rl isin use as an incoming repeater, conductors 64I are separated at thelower contacts of incoming transfer relay 6 I0. When the repeater is inuse as an outgoing repeater, conductors Bril are separated at the lowercontactsof outgoing transfer relay 66S. Conductors 64I are thusmaintained separated at any time when the repeater Rl (and consequentlythe associated in C-Ti) is in use, being joinedtogether at all othertimes to indicate an lidle condition of the trunk line to the associatedallotter.

Y I claim:

1. In a telephone system including a terminating automatic exchange, atandem automatic exchange, and` a'manual exchange, said exchanges beinginterconnected by trunk lines between the tandem exchange and the othersaid exchanges, trunk lines outgoing from the terminating exchange tothetandem exchange, each 'of said trunk lines having a repeater interposedtherein in the terminating exchange, the switching arrangement in thetandem exchange being such that the dialing oi a given number of digitsafter seizure of one of said trunk lines causes connection to beextended through the tandem exchange to the manual exchange, while theextending of a connection through the tandem exchange to a subscriberlineA thereof requires the dialing of a greater number of. digits,circuit arrangements eiiective on all calls outgoing from theterminating exchange to or through the tandem exchange for relayinganswered supervision back to the concerned repeater in the terminatingexchange,

a digit counter in said repeater eiective to count a sufficient numberof the digits dialed after such repeater is seized to determine whetherthe call is a manual-exchange call or is for a subscriber lineof thetandem exchange, means including means rendering it controlled by saiddigit counter according to the number of digits counted thereby, forreversing the current flow toward the calling line responsive to thereceived answered supervision, and circuit arrangements connected' withsubscriber lines of the terminating exchange for exacting a charge forthe calls made therefrom responsive to such current reversal.

2. In an automatic telephone system, links, automatic switchingapparatus for extendmg connections from calling lines to said links,other automatic switching apparatus including means rendering itresponsive to series of digit impulses dialed after connection isextended to any one of said links, for completing the connection to adesired called line, certain of said connections being of one class andrequiring the dialing of a given number of digits after connection hasbeen extended to one of said links, other of said connections being oianother class and requiring the dialing of a greater number of digitsafter the connection has been extended to one of said links,charge-exacting means connected with certain of said calling lines,means including means rendering it responsive to the setting up of aconnection through any one of said links from any one oi said certainlines, for operating said charge-exacting means or not, depending uponthe class of the connection, said operating means including a digitcounter eiiective to count a sucient number of the digits dialed afterlconnection is made to one of said links to determine the class of theconnection.

3. In an automatic telephone system, links, automatic switchingapparatus for extending connections from calling lines to said links,other automatic switching apparatus including means rendering itresponsive to series of digit impulses dialed after connection isextended to any one of said links, for completing the connection to adesired called line, certain or said connections being of one class andrequiring the dialing of a given number of digits after connection hasbeen extended to one oi said links, other of said connections being ofanother class and requiring the dialing oi 'a 'greater number of digitsafter the connection has been extended to one of said links, controlmeans in any of said links including means rendering it responsive toreceived answered supervision, for reversing the current now toward thecalling line, or not, depending upon the class of the connection, saidcontrol means including a digit counter effective to count a sufficientnumber of the digits dialed after connection is made to one of saidlinks to determine the class of the connection.

e. In an automatic telephone system, lines ci two classes, links,automatic switching apparatus for extending connections from callinglines to said links, other automatic switching apparatus including meansrendering it responsive to series of digit impulses dialedaiterconnection is extended to any one o said links, for completing theconnection to any desired called line of either class, charge-exactingrmeans connected with certain of said calling lines, control means in- Ycluding means rendering it responsive to the setting up oi a connectionthrough any one of said links from any one of said certain lines, foroperating' said charge-.exacting means or not, depending upon the classof the line called, said control means including digit-responsive meansoperable after connection is made to one of said links to determine theclass of the connection.

5. In a telephone system including a terminating automatic exchange, atandem automatic ex- 21 change, and a manual exchange, said exchangesbeing interconnected by trunk lines between the tandem exchange and theother said exchanges,

each trunk line outgoing from the terminating exchange to the tandemexchange having a repeater interposed therein in the terminatingexchange, the switching arrangement in the tandem exchange being suchthat the dialing of a given number of digits after seizure of one ofsaid trunk lines causes connection to be extended i through the tandemexchange to the manual exchange, while the extending of a connectionthrough the tandem exchange to a subscriber line thereof requires thedialing of a greater number of digits, circuit arrangements eiective onall calls outgoing from the terminating exchange to or through thetandem exchange for relaying answered supervision back to the concernedrepeater in the terminating exchange, a digit counter in said repeatereiective to count a sufcient number of the digits dialed after suchrepeater is seized to determine whether the call is a manual-exchangecall or is for a subscriber line of the tandem exchange, and meansincluding means rendering it controlled by said digit counter accordingto the number of digits counted thereby, for reversing, or notreversing, the current ilow toward the calling line responsive to thereceived answered supervision.

6. In a telephone system including a terminating automatic exchange, atandem automatic exchange, and a manual exchange, said exchanges beinginterconnected by trunk lines between the tandem exchange and the othersaid exchanges, trunk lines outgoing from the terminating exchange tothe tandem exchange, each of said trunk lines having a repeaterinterposed therein in the terminating exchange, the switchingarrangement in the tamden exchange being such that the dialing of agiven number of digits after Vseizure of one of said trunk lines causesconnection to be extended through the tandem exchange to the manualexchange, while the extending of a connection through the tandemexchange to a subscriber line thereof requires the dialing of a greaternumber of digits, circuit arrangements effective on all calls outgoingfrom the terminating exchange to or through the tandem exchange forrelaying answered supervision back to the concerned repeater in theterminating exchange, a digit counter in said repeater effective tocount a sufficient number of the digits dialed after such repeater isseized to determine Whether the call is a manual-exchange call or is fora subscriber line of the tandem exchange, and means including meansrendering it controlled by said digit counter according to the number ofdigits counted thereby, for exacting a charge if the connection has beencompleted to a subscriber line of the tandem exchange, but not if it hasbeen completed to the manual exchange.

PIEPv BAKKER.

REFERENCES CITED The following references are lof record in the le ofthis patent:

UNITED STATES PA'I'ENTS Number Name Date Y 1,337,782 Lundell Apr. 20,1920 1,415,001 Martin May 2, 1922 1,667,915 Wicks May '1, 1928 1,675,310Y Saville June 26, 1928 1,855,724 Nelson Apr. 26, 1932 1,855,779 TharpApr. 26, 1932A 1,917,884 Hague July 11, 1933 1,944,269 Raynsford et al.Jan. 23, 1934 2,192,02'5 Busch Feb. 27, 1940 2,226,731 Lomax Dec. 31,1940

